The invention relates to a refrigerant compressor apparatus comprising a drive motor, a compressor driven by the drive motor and having several cylinders arranged in a V shape and a compressor shaft bearing eccentrics for driving pistons operating in the respective cylinders.
Refrigerant compressor apparatuses of this type are known from the state of the art. With these the eccentrics are normally designed such that one eccentric serves to drive several cylinders in order to achieve a solution which is, on the one hand, of a compact construction and inexpensive.
Refrigerant compressor apparatuses of this type do, however, have the disadvantage of an uneven running when there is any deviation from an ideal V angle of 360xc2x0 divided by the number of cylinders.
The object underlying the invention is to improve a refrigerant compressor apparatus of the generic type in such a manner that as smooth a running as possible can be achieved at any desired V angle.
This object is accomplished in accordance with the invention, in a refrigerant compressor apparatus of the type described at the outset, in that the cylinders are arranged at a V angle of less than 90xc2x0, that the compressor shaft is mounted with only two bearing sections thereof in corresponding compressor shaft bearings, that the eccentrics are arranged between the bearing sections and that a separate eccentric is provided for each piston and this is arranged at a distance from the other individual eccentrics for the respectively other pistons.
The advantage of the inventive solution is to be seen in the fact that as a result of the independent arrangement of the eccentrics their rotary position relative to one another can be adjusted as required and that, as a result, a very smooth running can be achieved irrespective of the desired V angle due to free selectability of the angular position of the individual eccentrics relative to one another.
At the same time, the advantage of the simple type of construction is, however, still retained, in particular, the simple mounting with only two bearing sections of the compressor shaft.
It is particularly favorable, in order to be able to mount individual, undivided piston rods on the eccentrics, when the individual eccentrics are separated from one another by intermediate elements which have in the direction of an axis of rotation a length which corresponds at least to a width of a piston rod.
As a result of such intermediate elements, the sliding on of the undivided piston rods can be made substantially easier since a reorientation of the piston rod for sliding the same onto the next following intermediate element is possible after each eccentric.
In this respect, it is particularly favorable when the compressor shaft has between two consecutive eccentrics intermediate elements with a cross-sectional shape which extends in a radial direction in relation to the axis of rotation at the most as far as the closest one of two casing surfaces, of which one is the casing surface of the one eccentric and the other the casing surface of the other eccentric of the two consecutive eccentrics.
In order to bring about an optimum lubrication it is preferably provided for the compressor shaft to have a lubricant channel coaxial to the axis of rotation, wherein transverse channels for the lubrication of running surfaces of the eccentrics preferably branch off the lubricant channel in the area of each eccentric.
The lubricant bore is likewise preferably designed such that transverse channels branch off it for the lubrication of the bearing sections thereof.
With respect to the V angle provided between the cylinders it has merely been assumed thus far that this is smaller than 90xc2x0.
It is particularly advantageous when the cylinders arranged in a V shape form with one another a V angle of less than 70xc2x0. A particularly narrow type of construction can be achieved when the cylinders arranged in a V shape form with one another a V angle of approximately 60xc2x0 or less.
With all these solutions, with which the V angle is smaller than 70xc2x0, it is provided, in particular, for each of the eccentrics to be arranged in relation to the other eccentrics so as to be turned through an angle with respect to an axis of rotation of the compressor shaft.
A particularly favorable solution provides for the eccentrics to form pairs which are arranged so as to follow one another in the direction of the axis of rotation of the compressor shaft, wherein the eccentrics forming one pair are arranged so as to be turned relative to one another through an angle of 360xc2x0 divided by the number of cylinders plus the V angles and, in particular, each of the eccentrics of one pair is associated with one of two cylinders arranged in the V angle in relation to one another.
This solution has the great advantage that it brings about a compact construction since respective eccentrics following one another are associated with respective cylinders arranged in a V shape in relation to one another and are in a position to drive these with as smooth a running as possible.
In this respect, it is particularly favorable when the first eccentrics of each of the pairs and the second eccentrics of each of the pairs are arranged so as to be respectively turned through 180xc2x0 in relation to one another so that they operate in opposite directions to one another.
With all these solutions it is preferably provided for two respective eccentrics following one another to be associated with two respective cylinders arranged in a V shape in relation to one another in the case of all the eccentrics of the compressor shaft so that eccentrics arranged to follow one another are associated alternatingly with cylinders arranged on different sides.
One particularly advantageous solution provides for the compressor to comprise at least four cylinders and for the compressor shaft to comprise at least four separate eccentrics arranged at a distance from one another.
With respect to the use of individual cylinders no further details have so far been given. One particularly favorable embodiment of an inventive refrigerant compressor apparatus provides for the compressor to have a low pressure stage comprising at least one cylinder and a high pressure stage comprising at least one cylinder.
The high pressure stage and the low pressure stage are preferably subdivided such that one row of the cylinders arranged in a V shape forms the low pressure stage and the other row of the cylinders the high pressure stage.
With respect to the cylinder volumes of the low pressure stage and the high pressure stage no details whatsoever have so far been given. The cylinder volumes could, for example, be the same and it would be possible to adjust the capacities of high pressure stage and low pressure stage on account of the different eccentricity.
It has, however, proven to be particularly favorable when the eccentricity of the eccentrics with respect to the axis of rotation is the same and when the sum of the cylinder volumes of the low pressure stage is greater than the sum of the cylinder volumes of the cylinders of the high pressure stage so that an adjustment of high pressure stage and low pressure stage is brought about via the sum of the cylinder volumes.
One particularly favorable embodiment of the inventive solution provides for the low pressure stage to be reduced in capacity, in particular, to be switched off with respect to its compression effect. This is especially advantageous when a regulation of the capacity of the inventive refrigerant compressor apparatus is desired and, in particular, with a low cooling capacity the low pressure stage which is not, as such, required can be reduced in its capacity or switched off with respect to its compression effect in order to reduce the power input of the compressor.
Such a switching off of the low pressure stage may be realized in the most varied of ways. For example, it would be conceivable to have the low pressure stage operating free from compression, i.e. such that no compression at all of the refrigerant takes place.
Another possibility would be to open a bypass line to the low pressure stage.
A particularly favorable solution provides for a capacity regulation valve to be arranged on the suction side of the low pressure stage and for a valve which opens when a capacity regulation valve is active to be arranged between a low pressure connection of the compressor and a suction side of the high pressure stage.
A valve of this type may, for example, be actively controlled.
A particularly simple solution does, however, provide for the valve between the low pressure connection of the compressor and the suction side of the high pressure stage to be a check valve which opens automatically when a capacity regulation valve is active, dependent on the resulting difference in pressure, so that a targeted control of this valve between the low pressure side of the compressor and the suction side of the high pressure stage is not necessary and can be omitted.
In addition, a check valve has the advantage that this opens automatically when the pressure on the suction side of the high pressure stage is equal to or lower than the pressure at the low pressure connection and so no additional measures whatsoever are required for the exact control of this valve in the case of such pressure ratios.
With respect to the cooling of the drive motor, no further details have been given in conjunction with the preceding explanations concerning the individual embodiments.
It would, for example, be conceivable to cool the drive motor by means of the surrounding air or by means of the suction gas.
A particularly advantageous embodiment provides for the drive motor of the compressor to have the refrigerant flowing from the low pressure stage to the high pressure stage flowing through it and to be cooled as a result of this.
In this respect it is possible, in the case of any switching off of the low pressure stage, not to guide the refrigerant flowing directly from the low pressure connection to the suction side of the high pressure connection through the drive motor since, in this case, it can be assumed that the power requirements of the drive motor are, in any case, so low that the waste heat resulting in the drive motor can be discharged by means of the surrounding atmosphere or due to the coupling of the interior via the refrigerant not automatically guided through the interior.
A particularly favorable solution which in any case ensures an adequate cooling of the drive motor provides for the drive motor of the compressor to have the refrigerant entering the high pressure stage flowing through it, i.e. for the refrigerant which enters the high pressure stage to essentially flow through the drive motor, as well, and thus always ensure an adequate cooling of the drive motor.
In order to be able to provide a three-phase motor as drive motor it is preferably provided for a converter to be arranged on the drive motor, wherein the converter is preferably arranged on the drive motor such that its power components are thermally coupled to a housing of the drive motor.
Such a coupling to the housing of the drive motor may be achieved in a simple manner in that the power components are either coupled to an intermediate element or are arranged directly on the housing of the drive motor.
In order to ensure an adequate heat discharge it is provided, in particular, in the case of a drive motor cooled by the refrigerant for a housing part thermally coupled to the power components of the converter to be in thermal contact with the refrigerant, preferably with the stream of refrigerant flowing through the drive motor. As a result, an effective coupling of the amount of heat resulting in the power components of the converter to the refrigerant and thus an efficient discharge of the same is ensured.
A particularly advantageous arrangement of the converter, in particular, with a view to a compact and narrow type of construction of the inventive refrigerant compressor apparatus provides for the converter to be arranged on a side of the housing of the drive motor located opposite the compressor.
A refrigerant compressor apparatus operating according to the invention may be operated particularly advantageously, especially with a view to the energy consumption, when the drive motor is speed controlled, wherein a speed control of the drive motor preferably takes place with consideration of the cooling capacity required.
For example, a control is provided for the speed control of the drive motor which controls the speed of the drive motor in accordance with the required cooling capacity.
The inventive control which controls the speed of the drive motor may be used particularly advantageously for regulating the temperature of a medium to be cooled with the inventive refrigerant compressor apparatus, wherein the control detects the temperature of the medium to be cooled and controls the speed accordingly.
A particularly precise regulation of the temperature of the medium to be cooled is brought about when the control operates the drive motor free from any running interruptions and the entire temperature regulation is brought about exclusively via the speed and, where applicable, switching off of the low pressure stage.
Only in the case of a minimum cooling capacity of the inventive refrigerant compressor apparatus, which is less than 5% of the maximum cooling capacity, will a temporary interruption in the running of the drive motor be brought about during the regulation of the temperature of the medium to be cooled since, in this case, the heat input into the medium to be cooled is so slight that a precise regulation is also possible during a temporary interruption in the running of the drive motor.
It is, in addition, particularly expedient when the control controls the speed of the drive motor in accordance with ambient temperature.
Furthermore, an additional, advantageous development of the inventive refrigerant compressor apparatus provides for a control to be provided which switches off the low pressure stage when the cooling capacity falls below a predeterminable capacity. As a result, the possibility is created, in particular, in a simple manner of reducing the power to be supplied by the drive motor for the operation of the compressor, in addition, in the cases where such a slight cooling capacity is required that it can be supplied solely by the high pressure stage of the compressor.
Preferably, this likewise takes place as a function of the ambient temperature. A particularly favorable solution provides for the control for,the speed of the drive motor and for the switching off of the low pressure stage to be the same.
No further details have been given in conjunction with the preceding description of the inventive refrigerant compressor apparatus as to how this is intended to be operated. One advantageous embodiment provides for a liquid supercooler to be associated with the refrigerant compressor apparatus.
Those skilled in the art will appreciate that the term supercooler may be used interchangeably with the terms subcooler, undercooler, and overcooler.
In order to keep the type of construction of the refrigerant compressor apparatus likewise as compact as possible, it is preferably provided for the liquid supercooler to be arranged on a side of the compressor located opposite the drive motor.
The liquid supercooler is preferably designed such that it vaporizes liquid refrigerant for the liquid supercooling and this vaporized refrigerant enters the refrigerant flowing to the high pressure stage.
In order to bring about an optimum cooling of the drive motor, it is preferably provided for the refrigerant vaporized by the liquid supercooler to flow through the drive motor on its way to the high pressure stage.
The vaporized refrigerant is preferably supplied to the medium pressure channel prior to flowing through the drive motor.
A solution which is particularly advantageous with respect to the adequate cooling of the drive motor provides for the liquid supercooler to be controllable in accordance with a temperature of the drive motor. The detection of the temperature of the drive motor is preferably brought about via a detection of the temperature of the housing of the drive motor.
A particularly favorable solution, in particular, for the efficient cooling of the converter provides for the liquid supercooler to be controllable in accordance with the temperature of the part of the housing of the drive motor bearing the converter.
In order, however, to avoid condensed water forming in the area of the drive motor, it is preferably provided for the liquid supercooler to be controlled such that it maintains a minimum temperature of the part of the housing bearing the converter, wherein the minimum temperature of the part of the housing bearing the converter is selected such that no condensation whatsoever of moisture from the ambient air can occur.
For example, it is provided for the control of the liquid supercooler to be brought about in such a manner that the part of the housing bearing the converter remains at a temperature of at least 10xc2x0 centigrade, preferably at least 20xc2x0 centigrade.
Furthermore, it is preferably provided for the liquid supercooler to be controlled such that the maximum temperature of the part of the housing bearing the converter does not exceed a predetermined temperature. This predetermined temperature is at approximately 60xc2x0 centigrade, preferably approximately 50xc2x0 centigrade.
Additional features and advantages of the invention are the subject matter of the following description as well as the drawings illustrating one embodiment.